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Mitosis Aim#12: What are the stages of the Cell Cycle? 1. Cell Size: http://learn.genetics.utah.edu/content/begin/cells/scale/ a. Are large organisms, such as redwood trees and elephants, large because they contain extra large cells or just more standardsized cells? Explain. More standard sized cells b. Why do cells have a size limit? Smaller cells are more efficient (easier to control) c. What happens when a cell reaches its size limit? It can divide Mitosis d. Why do cells divide? Reproduction Replace cells Growth Regulation e. Why are smaller cells more efficient? Small cells = Larger Surface Area/Volume ratio Makes metabolic processes (like regulation and transport) much more efficient 2. How do different types of cells divide? Prokaryotes vs. Eukaryotes: Why is there a difference in the cell division between prokaryotes and eukaryotes? Prokaryotes do not have membrane bound organelles (like a nucleus) 3. Mitosis vs. 1 Cell divides into 2 identical diploid (2n) daughter cells Body Cells (muscle, skin, liver, etc) Meiosis 1 cell divides into 4 haploid (n) daughter cells with 1/2 DNA Sex cells (gametes) Mitosis 4. Structure of a Chromosome: a. Chromatin Thin, Relaxed DNA (spaghetti) found in a cell NOT dividing b. Chromatid One arm of a chromosome Sister Chromatids-identical, replicated DNA c. Chromosome Condensed DNA (ready for cell division) d. Gene DNA Chromosome e. Homologous Chromosomes - A pair of MATCHING chromosomes - Same Size, Same Centromere position, Same genes in the same locations Genes match but do not have to be identical!!! Humans have 46 chromosomes in body cells (made up of 23 pairs of Homologous Chromosomes (1 of each pair comes from Mom, and 1 of each pair comes from Dad) Mitosis Science History Break Has anyone ever heard of Henrietta Lacks? http://www.cbsnews.com/news/theimmortalhenriettalacks/ Why are HeLa cells so special? What is the controversy over using HeLa cells? 5. Stages of Cell Cycle: a. Interphase: "In between" (not dividing) G1: Growth/Life Processes (MR. STRANGE) S: DNA Replication G2: Prep for Mitosis (Centrioles) M Phase: Mitosis: Nuclear Cell Division PMAT http://vcell.ndsu.nodak.edu/animations/mitosis/movieflash.htm Cytokinesis: "Cytoplasm splits Checkpoints: points in the cell cycle where the cell "checks" its progress so far. Mitosis 6. Why is DNA Replication so important? Maintains the CORRECT chromosome number to make a new daughter cell 7. Mitosis: (PMAT) 1. Prophase (Pro- 1st) a. Strands of chromosomes begin to condense and become visible b. The nucleoli disappear c. Spindle fibers begin to form in the cytoplasm, extending from one centrosome to the other. d. The nuclear membrane begins to disintegrate. Prometaphase Mitosis Mitosis: (PMAT) 2. Metaphase (middle) a. Chromosomes line up single file along the metaphase plate (equator - middle) b. Centrosomes are at opposite poles of the cell c. Spindle fibers run from centrosomes to the centromeres of the chromosomes Mitosis: (PMAT) 3. Anaphase: (away) a. The centromeres of each chromosome separate away b. Spindle fibers begin to pull the sister chromosomes apart (chromatids) c. Shortest phase Mitosis Mitosis: (PMAT) 4. Telophase:(two nuclei) a. Chromosomes cluster at opposite ends of the cell, and the nuclear membrane reforms. b. supercoiled chromosomes begin to unravel and to return to their pre-cell division condition as long, threadlike strands (chromatin). Mitosis: (Animal Cell) 5. Cytokinesis: a. division of the cytoplasm b. Animal cells - a cleavage furrow forms down the middle of the cell and the cytoplasm pinches inward separating two daughter cells c. Plant cells - Cell plate forms down the middle of the cell (cell wall) Mitosis Interphase: Interphase: - More than 90% of the life cycle of a cell - Chromatin - Nuclear membrane is visible G1 - Cell Growth S - DNA replication G2 - Preparation for mitosis Same Chromosomes (Identical DNA) Smaller in size Mitosis Mitosis Identify at least 1 cell in each of the following stages: interphase prophase metaphase anaphase telophase What percentage of cells are in interphase? What percentage of cells are in mitosis? Does this make sense? Why?
